1. Field of the Invention
The present invention relates to a tube pump and a printer provided with the tube pump.
2. Description of the Related Art
An ink-jet printer performs a cleaning operation in which ink is ejected from an ejection port in order to prevent ejection failures at a print head or other faults. The cleaning operation includes closing a recording head with capping means and applying a negative pressure to the inside of the capping means using the tube pump.
Known examples of such a tube pump used in a printer include a tube pump that receives, from a groove wall of a roller-supporting groove, a force of action that displaces a roller from a pump operation position to a release operation position while the roller stops rotating or turning.
As illustrated in FIG. 13, the existing tube pump includes a tube 151, a pump frame 144, a pump wheel 142 rotated by a motor, and rollers 143a and 143b that move along roller supporting grooves 142a and 142b formed in the pump wheel 142. Letter-L-shaped fastening grooves 144a and 144b are formed in the pump frame 144. Guide members 153a and 153b made of an elastic material and protruding toward the center of the pump wheel 142 are locked on the fastening grooves 144a and 144b. 
As illustrated in FIG. 13, when the pump wheel 142 is rotated in the direction of an arrow P, the rollers 143a and 143b move toward the axis of the pump wheel 142 and rotate or turn in the direction of an arrow P while keeping in the release operation state in which the rollers 143a and 143b slightly come into contact with the tube 151. At this time, in accordance with the rotation of the pump wheel 142, the pair of guide members 153a and 153b act so as to guide the rollers 143a and 143b along the respective roller supporting grooves 142a and 142b in the backward direction of wheel rotation.
However, the above-described existing tube pump has a problem as follows. Due to elastic deformation of the guide members 153a and 153b at the rotation or rolling of the rollers 143a and 143b, long time use of the tube pump degrades the guide members 153a and 153b, which hinders positional changes of the rollers 143a and 143b between the pump operation position and the release operation position and lowers the pump performance.